Malignant gliomas, the most common form of central nervous system (CNS) cancers, is currently considered essentially incurable. Among the various malignant gliomas, anaplastic astrocytomas (Grade III) and glioblastoma multiforme (GBM; Grade IV) have an especially poor prognosis due to their aggressive growth and resistance to currently available therapies. The present standard of care for malignant gliomas consists of surgery, ionizing radiation, and chemotherapy. Despite recent advances in medicine, the past 50 years have not seen any significant improvement in prognosis for malignant gliomas. Wen et al. Malignant gliomas in adults. New England J Med. 359: 492-507, 2008. Stupp et al. Radiotherapy plus concomitant and adjuvant temozolomide for glioblastoma. New England J Med. 352: 987-996, 2005.
The poor response of tumors, including malignant gliomas, to various types of chemotherapeutic agents are often due to intrinsic drug resistance. Additionally, acquired resistance of initially well-responding tumors and unwanted side effects are other problems that frequently thwart long-term treatment using chemotherapeutic agents. Hence, various analogues of chemotherapeutic agents have been prepared in an effort to overcome these problems. The analogues include novel therapeutic agents which are hybrid molecules of at least two existing therapeutic agents. For example, cisplatin has been conjugated with Pt-(II) complexes with cytotoxic codrugs, or conjugated with bioactive shuttle components such as porphyrins, bile acids, hormones, or modulators that expedite the transmembrane transport or the drug accumulation within the cell. (6-Aminomethylnicotinate) dichloridoplatinum(II) complexes esterified with terpene alcohols were tested on a panel of human tumor cell lines. The terpenyl moieties in these complexes appeared to fulfill a transmembrane shuttle function and increased the rate and extent of the uptake of these conjugates into various tumor cell lines. Schobert et al. Monoterpenes as Drug Shuttles: Cytotoxic (6-minomethylnicotinate) dichloridoplatinum(II) Complexes with Potential to Overcome Cisplatin Resistance. J. Med. Chem. 2007, 50, 1288-1293.
Perillyl alcohol (POH), a naturally occurring monoterpene, has been suggested to be an effective agent against a variety of cancers, including CNS cancer, breast cancer, pancreatic cancer, lung cancer, melanomas and colon cancer. Gould, M. Cancer chemoprevention and therapy by monoterpenes. Environ Health Perspect. 1997 June; 105 (Suppl 4): 977-979. Hybrid molecules containing both perillyl alcohol and retinoids were prepared to increase apoptosis-inducing activity. Das et al. Design and synthesis of potential new apoptosis agents: hybrid compounds containing perillyl alcohol and new constrained retinoids. Tetrahedron Letters 2010, 51, 1462-1466.
Co-owned U.S. Patent Publication No. 20130203828 disclosed various perillyl alcohol derivatives such as perillyl alcohol carbamates. For example, the perillyl alcohol derivatives include perillyl alcohol conjugated with a therapeutic agent such as dimethyl celocoxib (DMC), temozolomide (TMZ) or rolipram.
There is still a need for perillyl alcohol derivatives with improved properties for transdermal or topical application, as well as use the derivatives in the treatment of cancers such as malignant gliomas, skin cancers as well as precancerous skin conditions.